Is it permissible for a committed sister to attend a university lecture with female students and a male instructor who jokes and gets to know them and talks about things other than the lesson, with her response limited only to the question asked?

The default rule is that it is permissible for a man to teach girls and women if Islamic guidelines are observed, such as the absence of khalwa (private seclusion), adherence to the legal hijab, lowering the gaze, limiting conversation to what is necessary, and not speaking in a soft and alluring manner.

As for transgressing these guidelines by joking and engaging in unnecessary conversation, it is a means to fitna (temptation), a cause of corruption, and a gateway for Satan. Therefore, one must refrain from it and limit conversation with non-mahram individuals to what is necessary. It is incumbent upon a committed woman to clarify the danger of excessive conversation with non-mahram men. If they do not desist, it is preferable to seek others.